Method and apparatus for heat removal by mercury



Nov; 4, 1930, B. L. NEWKIRK METHOD AND APPARATUS FOR HEAT REMOVAL BY MERCURY Filed Aug. 4, 1927 H is Attorney cury vapor boilers. It isi1 therefore, a poorv Patented Nov. 4, 19850 UNITED STATES PATENT orrics BURT I. OF SCHENEC'IADY, NEW YORK, ASSIGNOB 130 5 I d I p COMPANY, A CORPORATION OF NEW YOBK mn'rnon mu hummus non HEAT mover. BY mmcumr Application filed August .4, 1927. Serial myaioaoi.

In connection with a paratus, such as boilers, for the removal of cat by mercury, that is to say, in connection with boiler apparatus for vaporizing mercury, it is essential, for known reasons, to reduce to a minimum the amount of mercury required for operation. On the other hand, however, it is essential that sufficient mercury be rovided to remove adequately the heat from t e wall of the boiler tube or other container which is exposed to the fire or the hot gases, or otherwise the tube or other container will be burned or'distorted.

Mercury vapor has a very low specific heat, and only a moderate density when used at the low pressures now employed in known" meragent for the removal of cat from any surface. On this account it has been considered necessary heretofore in thedesign of mercury boilers, so to construct them that always there would be liquid mercury washingthe walls from which any considerable amount of heat was to be removed.

This has been a limiting factor in reducing the amount of mercury required in the operation of mercury vapor generating apparatus. The object of my present invention is to provide an improved method and apparatus whereby the amount of mercury required in a mercury vapor generating apparatus for its safe operation may be still further reduced, and for a consideration of what I believe to be novel and my invention, attention is directed to the accompanying description and the claims appended hereto.

l have found that a mixture of mercury liquid and mercury vapor which mixture is predominantly vapor by volume is a fairly good agent for the removal oi heat from the Walls of a container, such as a boiler tube, it being substantially better than mercury vapor although not as good as liquid mercury. Ac cording to my invention, therefore, create a mixture of mercury liquid and mercury vapor, which by volume, and utilize such mixture in the removal of heat from the boiler tube or other container. The mixture is in the form of mercury vapor through which is distributed globules oi liquid mercury. li y predom} mixture is predominantlyvapor.

nantly vapor by volume, I mean mixtures wherein the percentage of liquid by volume is comparatlvely small. For example, I have found mixtureswherein the volume of liquid to vapor was of the order of1 to 2% I satisfactor It is to be understood, however, that t ese figures are given only by way of example and are not to be taken as limitations for my invention.

apparatus embodying my invention, I prefera In construction a mercury vapor generating ly so arrange it that those portions of the heating surfaces which must transmit large amounts of heat are cooled by liquid mercury,

the remaining surfaces being cooled by a mixture of mercury liquid and mercury vapor.

In carrying out the invention I use prefer ably also means to separate the minute liquid glo ules from the vapor before passing the vapor on to a turbine or other a paratus. This can be accomplished by centriihging or by causing the mixture to sweep over a sur face of liquid mercury, preferably so that the stream of the mixture changes direction in such manner that the globules of liquid tendmg more than the vapor to move in straight lines, strike a surface of liquid mercury and coalesce with it.

As one means of carrying out my invention 1 may employ a mercury container in the form of a long tube of comparatively small bore. By a long tube 1 mean a tube of the order of ten feet or more in length, and by a tube of comparatively small bore I mean a tube having an inside diameter of the order of 0.4 of an inch. For example I have found a tube ten feet long and havin an inside diameter of 0.38 of an inch satistactory. I then supply liquid mercury under suitable pressure to the lower end of the tube. this arrangement, the intense heat applied to the lower portion or? the tube causes vigorous ebullition and efiec-ts the formation of a mixture of mercury vapor and mercury liquid in the tube above the mercury liquid therein depressing the level of the liquid in the tube, This mixture, sweeping along the walls or? the upper portion of the tube, serves to remove the heat therefrom and vaporize some of the globules of mercury in the mixture.

With

l6 a level in the tube.

rising column of liquidand vapor a whirling motion which breaks up uid by v0 ume in the working mixture being extremely small. I

I may with advantage employ a special means or device in the tube or container to break up the liquid into small globules and to cause this mixture to sweep set or am 'nst the surfaces tobe cooled. or examp e, in the case of a long tube ofsmall here, I may use a twistedor helical stri in the tube which extends from a point in t e vicinity of the top of the tube to a is serves tojgive the the liquid, and

causes the liquid particles to make numerous contacts with the surfaces to be cooled.

A mixture of mercu liquid and mercury va or, as described, is e ective as an absorber of eat because any introduction of heat into a quantit of the mixture vaporizes some'of the liqui but does not increase the tem rature of the mixture. The presence 0 the globules of liquid gives the mixture a property which may be described as that of an infimtely great specific heat, in that the intro duction of a comparatively large amount of heat into the mixture may take place without raising the temperature to any appreciable extent. For example, a quantity of the mixture at 100 pounds pressure andcontaining 90 ercent iquid by weight could absor wit out increase in templerature about eight hundred times as much eat as would be re quired to raise the temperature of an equal volume of mercury vapor alone i. e. without liquid globules) fifty degrees Such a mixture, however, (being at 100 pounds per sq. in. absolute pressure and consisting of 10% vapor and 90% liquid by weight) would fill'a volume over fifty times as great as it would if it were all liquid. It follows, therefore, that by the use ofa mixture of this sort I accomplish two im ortant results in that first I provide a su stance which is very much superior to mercury vapor alone as an agent to remove heat from a surface, and second I provide a substance which is very much superior to the mercury liquid alone in its capacity to cover and remove heat from a large surface because of the relatively large volume of the mixture. I

These two roperties of the mixture, viz: capacity to a sorb a large amount of heat without increase in temperature and, large volume compared with that of the liquid, render this mixture very useful in reducing substantially the quantity of mercury liqui required in the operation of a mercury vapor generator.

In the draw-in wherein I have shown my invention applie to a wall screen for a fur- 'nace wall and 2 indicates oint below the liquid.

conduits 5 with 2; and Fig. 4 is a sectional view of a modification. Referring to the drawing, '1 indicates a furgenerally a wall screen in front of it. The wall screen comprises a number of sets of tubes,'each set being made up of Ion tubes 3 of comparatively small bore, the intfividualtubes of'each set bein welded or otherwise fastened together.

cats with a li uid supply conduit 4- and at their upper on s they communicate through a vapor drum 6.f, B repre- I sents the level of liquid mercury in drum 6; e endsof conduits 5 are ,turned upward so that the vapor enters thedrum at an angle with theradial direction whereby centrifuging action results. 7 indicates a conduit through'which mercury va r maybe drawn oil. from drum 6. Circulation of li uid from drum 6 to supply'conduit' 4 is e ected by means of a ipe '8 which connects the lower portlon of rum 6 to supply conduit 4. 6A indicates a grid toprevent the liquid mercury from being washed away from the entrance to the pipe 8 by the blast from conduit 5. The line A indicates an approximate normal level .of mercury liquid in tubes 3 when boiling is in progress, the portion of the tubes-below .At t eir lower ends the sets of tubes communithe line A containing mercury liquid while the portion above the line A contains a mixture of mercury liquid and mercu vapor. It will be understood that the liquiyle'vel in the tubes 8 ma vary to a considerable extent, the line A in icating, as stated above, what may be considered an approximate normal, level for satisfactory operation. Indrum 6 is a bafile 8! provided with openings 8" through which t e va r flows to conduit 7.

The level of liqui is maintained at A by the back pressure of and liquid in the tube above level A. he location of the level A in any tube 3 de ends upon the amount of heat being trans erred by that tube. If a small amount of heat is 'bein transferred, the level is high, but when the eat transfer isnear the capacit of the tube, level A is near the bottom of t e tube, The hydrostatic pressure due to difierence in level between level B in drum 6 and level A is required to drive the vapor and entrained 1i uid out of the tube. i

11 each tube is a twisted strip 9 which extends from a point in the region of the upper end of the tube to a point below the liquid level in the tube for to the rising column of liquid and vapor.

the mixture of vapor giving a whirling motion In using a wall screen of the type shown,

' advantage that by-t incomes V so that the tubes shall not become overheated above the liquid line A. To this end it is desirable that a large pro ortion of the total wall area of the furnace e covered by the screen, otherwise heated refractories may radiate an excessive amount of heat to thetubes. It is important also not to push the furnace and boiler too hard by'burning too Finally much coal in-a given furnace space. where the service is too severe to ermit, the use of tubes unprotcctedabove the liquid level A, refractories may be added and supported from the tubes themselves, in accordance with any known method so as to protect the tubes. 'Suchrefractories are indicated at 10 in Fig.

1', thesame being supported by suitable brackonly the advantage that it utilizes a smaller amount of mercurykbut' also the additional introduced into a" generator with fewer arts to be handled inmanufacture and with" ewer joints. In this connectionit will be understood that the'minimizing of the number of joints is a matter (if considerable-im ortance from a practical standpoint in that 1t serves to reducethe danger of leakage.

What I'claim as newand desire to-secure by Letters Patent of the United States, is

, 1. Thelmethodof transferring heat in a .mercuryvapor generatingapparatus which mahodg 'rhich c mfprises generating ua'ntly vapor by volume but not by wei using-this separating the vapor-from the liquid.

3 comprises generating an intimate mixture of mercury vapori'and finely divided mercury liquid which is predominantly yapor in volume but not in weight, andpassing such mixture along the heated surface to absorb heat therefrom. I I} 2. In a boiler for theitransfer of heat to mercury for generating. mercury vapor, the method which comprises utilizing an mtimate mixture ofjmercury vapor and finely divided mercu liquid as a' cat absorbing agent, said mixture,

3.. Inthe generationinfmercury va or the methodwhich com rises generating rst an intimatemixture o mercury vapor and finely divided Im'e'rcuryTli uid, which is predominantly jvapor by o ume but not by Wei ht, mixture to jabsorb. heat and t en 4.'In;the generation of mercury vapor the rst an vapor and finely intimate mixtureo niercu I 10b is predomidiv-idedfrnercury'{liquid w using the mixture to absorb heat and t en are fiat instead of nerating apparatus built inaccordance wit my invention has not euse-of lon tubes, the reqmred amount 'of heating su ace can be being predominantlyvaporin-volume' but not in weight;

--separating the vapor'ifrom the liquid by centrifuging.

'5. In a process for. generating mercury I vapor the method which comprises generating first an intimate mixture of mercury vapor and finely divided ercury liquid which is predominantly .vapor by volume, ,using the mixture separating the vapor from the liquid. by changing the direction of motion of the mixture.v f

ratus the combination of means for generating an intimate mixture of mercury vapor d1vided mercury'llquld, and means.

and finel for Slipp yingheat to said'mixture.

7. n a'mercury vapor generating apparatus, the combination of means for generating an intimate mixture of mercury vapor and finely divided mercury liquid, a heated surface, and means forefiectin the assage of said mixture into contact wi i' surface.

3..In a mercury vapor generating apparatus, the combination of means for generating an intimate mixture of mercury vapor and finely divided mercury liquid, and means to absorb'heat and then 6. In a mercury vaporgenerating appa-' sai heated Y for supplyingh'eat to said mixture,said firstnamed means comprising tubes of substantial length and" comparatively small bore.

r 9'. Inca. mercury vapor generating apparatus, the combination of means iorgenerating an'intimate mixture of mercury vapor and finely divided mercury liquid, said means comprising tubesof substantial length and comparatively small'bore, means for supplying heat to said tubes, and means for supplying liquid mercury to said tubes.

.10. In a mercury vapor generating apparatus, the combination of means for generating an, intimatemixture of mercury vapor and finelydivided mercury liquid, said means comprising substantially vertical tubes of.

substantial length and comparatively small bore, means for supplying heat to said tubes, and means for supplying liquid-mercury to said tubes. V

11. In amercury vapor generating apparatus, the combination of means for generating an intimate mixture of mercury vapor and finely divided mercury liquid, said means comprisin substantially vertical tubes of substantia length. and comparativel small bore, means for supplying heat to sai tubes means for supplying liquid mercu to said tubes, and means associated with sai tubes to aid in effecting generation of said mixture.

12. In a mercury vapor generating apparatus, the combinationof means for generatan intimate mixture of mercury vapor an finel divided mercury liquid, said means comprisi substantially vertical tubes of substant' length and comparatively small bore, means for supplying heat to said tubes for supplying quid mercury to sai 4 r i I v I,780,688

tubes, and means or separating the vapor from the mercury liquid after the mixture 88 passed out of said tubes.

13. In a mercury vapor generating appa ratus, the combination of means for generating an intimate mixture of mercury vapor and finely'divided mercury liquid which is predominantly vapor in volume but not weight, said means comprising tubesof substantial length and comparatively small here means for supplying heat to said tubes, and means for supplying liquid mercury to said tubes. 7 I Y 7 g .14. In a mercury vapor generating appa-' ratus, the combination of means for generating an intimate mixture of mercury vapor andfinely dividedli uid mercury, said means 1 comprising tubes, 0 substantial length and com aratively small bore, means for-supply? ing eat to said tubes, means for supplying liquid to said tubes, and means insaid tubes for im arting a whirling motion to the moving co umn of mercury liquid and mercury vapor in the tubes. I

15. In a mercury vapor generating apparatus, the combination of means for generating an-intimate mixture of mercury .vapor and finely divided mercury liquid, said means w comprisin substantially vertical tubes of 'substantia length and comparatively small stantially vertical tubes of substantial tubes for protecting suc bore,'means for supplying heat to said tubes, means for supplying liquid mercury to the lower ends of said tubes, and means in said tubes for inipartinga whirling motion to the rising column of mercury liquid and mercury vapor in the tubes.

16, In a mercury vapor'generating apparatus, the combination of afurnace'wall, means in front of said wall for eneratin an intimate mixture of mercury "quid an mercury vapor, said means comprising tubes of substantial length and comparativel small re, means for supplying heat to sai tubes, and means for s pplying liquid mercury to saildztlihles; I I

a mercury va or eneratin a aratus, the combination of a furnac e 3211, means in front ofsaid wall for eneratin an intimate mixture of mercury fiquid an mercury vapor, said means comprising subength and comparatively small bore, means for supplying liquid mercury to said tubes, and means in front of the uplper portions of said portions from intense heat.

In witness whereof, I have hereunto set my hand this 3d day of Au st, 1927.

. BUR L. N EWKIRK. 

